Compliant gripper mechanism for robotic magnetic tape cartridge handling system

ABSTRACT

The gripper mechanism is housed in a substantially rectangular box-like enclosure and includes a plurality of guide rails to align and support an object retrieved from an object storage location by the finger gripper mechanism. The finger gripper mechanism is attached to a carriage which functions to translate the finger gripper mechanism from a position proximate to the object storage location to a position within the enclosure. A degree of compliance between the gripper fingers and the object in the selected object storage location is provided by a centering spring that functions to couple the finger gripper mechanism to the carriage.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No.07/819,279 titled "Cartridge Positioning Mechanism for Robotic MagneticTape Cartridge Handling System" and filed on Jan. 13, 1992, U.S. patentapplication Ser. No. 07/820,099 titled "Tractor Mechanism for RoboticMagnetic Tape Cartridge Handling System" and filed on Jan. 13, 1992,U.S. patent application Ser. No. 07/819,782 titled "Finger GripperMechanism for Robotic Magnetic Tape Cartridge Handling System" and filedon Jan. 13, 1992.

FIELD OF THE INVENTION

This invention relates to automated object handling systems and, inparticular, to a lightweight magnetic tape cartridge gripper mechanismthat includes a compliant finger gripper positioning mechanism forretrieving magnetic tape cartridges from storage locations within anautomated magnetic tape cartridge library system.

PROBLEM

It is a problem in the field of automated object handling systems toproduce a robot mechanism that is inexpensive, lightweight, and whichoperates at a high rate of speed. A typical object handling systems isan automated magnetic tape cartridge handling system which operates tostore and retrieve a large number of magnetic tape cartridges of the3480-type format for an associated host processor. An example of such anautomated magnetic tape cartridge handling system is the 4400 AutomatedCartridge System (ASC) manufactured by Storage Technology Corporation ofLouisville, Colo. The 4400 Automated Cartridge System includes twoconcentric cylindrical arrays of magnetic tape cartridge storagelocations for storing a large number of magnetic tape cartridges. Eachcartridge storage location in the two cylindrical arrays opens into thespace between the two concentric cylindrical arrays.

The 4400 Automated Cartridge System is equipped with a robotic cartridgehandling mechanism that includes a support column located at the centerof the concentric cylinders and having a cartridge retrieval mechanismpositioning arm rotatably attached thereto. The rotatable positioningarm supports a cartridge retrieval mechanism that moves in the spacebetween the two concentric cylinders to access the magnetic tapecartridges stored in the cartridge storage locations in the twoconcentric cylinders. The cartridge retrieval mechanism includes agripper mechanism consisting of a pair of fingers that are driven by alead screw and a motor. The rotation of the lead screw causes the pairof fingers to tightly grasp a magnetic tape cartridge that is stored ina selected one of these cartridge storage locations. The force exertedby the fingers on the magnetic tape cartridge is of sufficient magnitudeto securely maintain the magnetic tape cartridge in a fixed alignmentwith reference to the gripper mechanism. In order to exert sufficientforce to prevent any movement of the magnetic tape cartridge, thegripper mechanism must be large, the motor required to drive the grippermechanism must be of substantial size and consumes a significant amountof power.

A significant disadvantage of such a robust gripper mechanism is thatits weight, being placed at the distal end of a rotating positioningarm, creates a sizeable force on the center pivot support column whichmust maintain the gripper mechanism in a precise orientation withrespect to the magnetic tape cartridge storage locations in the twoconcentric cylindrical arrays. As the weight of the gripper mechanismincreases, so must the mass of the rotating positioning arm increase inorder to support and precisely position the gripper mechanism. Anyincrease in the mass of these elements requires a commensurate increasein the size of the motors used to drive these elements which furtherlimits the speed with which these elements can be moved within theautomated cartridge library system. Therefore, it is desirable tominimize the size and weight of the gripper mechanism in order to enablea corresponding reduction in the size and mass of the other supportelements of the robotic cartridge retrieval mechanism. A reduction inthe complexity of the gripper mechanism also reduces the cost ofmanufacture and maintenance of such a mechanism. Therefore, it isdesirable to simplify and reduce the weight of the gripper mechanism ina object retrieval system, especially where the gripper mechanism isplaced at the distal end of an arm used to position the grippermechanism in front of an object storage location.

SOLUTION

The above described problems are solved and a technical advance achievedin the field by the compliant gripper mechanism, for an object handlingsystem that automatically positions the gripper mechanism in referenceto an object stored in a selected object storage location. Thisapparatus comprises a mechanically simple and lightweight grippermechanism for use with a robotic object handling system to retrieveobjects from a plurality of object storage locations. In particular, thegripper mechanism includes two fingers hingeably attached to a supportand operable by means of a spring to grasp an object with apredetermined amount of force and a solenoid to open the fingers andrelease the object. Also attached to the fingers is a loading linkagemechanism that exerts a closing force on the fingers in excess of thepredetermined closing force when the object is attempted to be removedfrom between the fingers. The loading linkage mechanism dynamicallyadjusts the magnitude of the force applied to the fingers as a functionof the force applied to the object to remove it from between thefingers. Therefore, the greater the force placed on the object by anexternal source, the greater the force applied by the loading linkagemechanism to retain the object between the fingers. The finger grippermechanism makes use of a spring and a simple lightweight solenoid tooperate the fingers and therefore requires little energy to operate,while the loading linkage mechanism requires no additional energy tooperate.

The gripper mechanism is housed in a substantially rectangular box-likeenclosure and includes a plurality of guide rails to align and supportan object retrieved from an object storage location by the fingergripper mechanism. The finger gripper mechanism is attached to acarriage which is moveable along one axis of the rectangular enclosureon a pair of tracks, which tracks are located one on each of twoopposite sides of the interior of the enclosure. The carriage rides onthese tracks and is transported from a retracted position entirelywithin the enclosure to an activated position juxtaposed to an openingin the enclosure by a tractor mechanism that makes use of a pair oftoothed belts, each belt being juxtaposed along the length of one of thetracks on which the carriage slides. The use of the two toothed beltsenables the precise positioning of the finger gripper mechanism andprevents the carriage from binding as it slides along the pair oftracks.

Interposed between the walls of the enclosure and the finger grippermechanism, extending from the opening into the interior of theenclosure, along each of the four interior corners of the enclosure, arelocated compliant guides which support the object transported by thecarriage with its finger gripper mechanism as the object is retrievedfrom its object storage location and retracted into the enclosure forrelocation by a robot arm mechanism. Each of these four compliant guidesconsist of an elongated L-shaped guide finger that is attached to theenclosure by a spring mechanism to enable the guide finger to translatein directions that are normal to the opening in the enclosure. The endof the guide fingers adjacent the opening in the enclosure are taperedin order to provide a funneling capability to account for misalignmentsbetween the object that is retrieved and the precise center lines of theenclosure.

The finger gripper mechanism is transported with the carriage to itsposition proximate to the opening in the enclosure where it encountersand grasps the object to be retrieved. The two fingers of the fingergripper mechanism close on the object to securely hold the object with aforce of predetermined magnitude. The tractor mechanism retracts thecarriage and finger gripper mechanism into the enclosure where theobject encounters the guide fingers of the four compliant guides, whichfunction to support the object as it is being retrieved into theenclosure. Any misalignment between the object and the enclosure iscompensated for by the guide fingers which translate in the direction ofthe misalignment when they encounter the object being retrieved, inorder to support the object and to guide it toward the center lineposition within the enclosure. The spring mechanism attached to each ofthe guide fingers enables the guide fingers to be translated to the edgeof the enclosure in order to capture the object as it is being retrievedfrom the object storage location. The spring mechanism also functions toautomatically reposition the object once it clears the object storagelocation to a position that is substantially centered within theenclosure.

A second degree of compliance between the gripper fingers and the objectin the selected object storage location is provided by a centeringspring that functions to couple the finger gripper mechanism to thecarriage. A misalignment between the gripper fingers and the object isfirst compensated for by the guides located in the enclosure. Whengreater than a predetermined force is created by the misalignment, theexcess force is transmitted through the finger gripper mechanism to thecentering spring which provides a certain additional amount ofcompliance. In particular, the finger gripper mechanism can move withrespect to the carriage in response to the transmitted force due to theuse of the centering spring that loosely couples the finger grippermechanism to the carriage. The finger gripper mechanism is repositionedby the guides when the object is retrieved into the enclosure.

Thus, this gripper mechanism is simpler in construction, lighter inweight than prior art gripper mechanisms and enables a correspondingreduction in the size and weight of the associated robotic grippermechanism positioning arm. The gripper mechanism is also designed to besimple to assemble without the use of fasteners.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates a perspective view of the gripper mechanism of thepresent invention;

FIG. 2 illustrates a perspective view of the gripper mechanism with theenclosure removed therefrom;

FIGS. 3 and 4 illustrate front and rear perspective views of the fingersection of the gripper mechanism absent the enclosure;

FIG. 5 illustrates an exploded view of the finger section of the grippermechanism;

FIG. 6 illustrates an exploded view of the tractor mechanism, guidefingers and enclosure;

FIG. 7 illustrates an end view of the opening in the enclosure and theguides contained in the enclosure:

FIG. 8 illustrates the interconnection of the finger gripper mechanismto the carriage;

FIG. 9 illustrates further details of the interconnection of thecarriage mechanism with the drive belts of the tractor mechanism;

FIG. 10 illustrates additional details of the finger gripper mechanism;and

FIG. 11 illustrates additional details of the interconnection of thetoothed belts.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrate perspective views and FIG. 7 illustrates an endview of the gripper mechanism of the present apparatus. Grippermechanism 100 is typically attached to a robotic positioning mechanism,such as at the distal end of a rotating positioning arm (R) and is usedto retrieve objects 120 from object storage locations 0. In thepreferred embodiment disclosed herein, gripper mechanism 100 is attachedto a robotic cartridge retrieval mechanism R and retrieves magnetic tapecartridges 120 from cartridge storage locations 0. Enclosure 101completely encloses the moving parts of the gripper mechanism 100 andfunctions as a support for the various elements contained therein as isdescribed in detail below. A set of Cartesian coordinates is drawn onFIGS. 1 and 2 in order to assist with the understanding of theinterrelationship of the various elements contained in this apparatus.

Enclosure 101 consists of a substantially rectangular box-like structurethat contains an opening in one end (A) thereof, which opening comprisesa plane in the x and y coordinate directions. The opening is selected tobe large enough to enable the gripper mechanism to pass the magnetictape cartridge 120 through the opening with sufficient extra roomprovided in both x and y directions to account for any misalignmentbetween the center lines V_(c), H_(c) of the opening in the enclosure101 of the gripper mechanism and the center lines of cartridge 120 as itis stored in cartridge storage location 0. It is expected that the robotarm mechanism R positions the enclosure 101 with its included gripperfingers 111, 112 juxtaposed to a cartridge 120 to be retrieved from aselected cartridge storage location 0 with a fairly high degree ofprecision. However, since the robot arm mechanism R is a mechanicalapparatus, it is expected that a certain amount of misalignment betweenthe gripper fingers 111, 112 and cartridge 120 is encountered duringnormal operation. The gripper fingers 111, 112 and their associatedmechanisms (collectively called finger gripper mechanism 127) aredesigned to be flexibly compliant in order to grasp the cartridge 120and, at the same time automatically realign to compensate formisalignment between the vertical center line V_(c) and the horizontalcenter line H_(c) of gripper fingers 111, 112 and the correspondingcenter lines (not shown) of cartridge 120. When gripper fingers 111, 112grasp cartridge 120 and begin to extract cartridge 120 from cartridgestorage location 0, cartridge 120 is automatically aligned with theopening in enclosure 101 and centered therein. This is accomplished bythe use of a plurality of compliant guides 131-134 which function toguide cartridge 120 into the opening and center it therein oncecartridge 120 has been completely withdrawn from cartridge storagelocation 0 and drawn in its entirety into enclosure 101. The guides131-134 also function to support cartridge 120 to thereby reduce theamount of gripper force required to be produced by finger grippermechanism 127 and to reduce the required precision and rigidity offinger gripper mechanism 127.

Complaint Guides

The guides 131-134 (FIGS. 6 and 7) consist of a plurality of springloaded tapered elements, in the preferred embodiment being four guides,each of which is located along an interior corner edge of enclosure 101and extends from opening end A of enclosure 101 to interior rear end Pof enclosure 101. In particular, the guides 131-134 extend from theopening end A of enclosure 101 a distance sufficient to supportcartridge 120. The guides 131-134 are attached to enclosure 101 viafasteners (not shown) and standoffs 182 to be fixed in a position thatcreates a substantially rectangular pocket to receive the substantiallyrectangular cartridge 120 and reposition cartridge 120 in a centeredlocation once it is retrieved into enclosure 101. As illustrated inFIGS. 6 and 7, guides 131-134 include L-shaped guide fingers 141-144,attached to spring mechanisms 135-138 which are in turn attached toattachment plates 145-148. These elements are illustrated as a unitarystructure, but can be separate interconnected elements. The distal end Aof the guide fingers 141-144 adjacent to the opening in enclosure 101include a tapered segment 151-154 to provide an increased aperture tothereby funnel cartridge 120 into the opening of enclosure 101 as it iswithdrawn from object storage location 0. Spring mechanisms 135-138 aredeformable via compression to enable tapered segments 151-154 to alignwith cartridge 120 in object storage location 0. Spring mechanisms135-138 enable guide fingers 141-144 to reposition in both x axis and yaxis directions in response to cartridge 120 contacting guide fingers141-144.

Thus, when gripper fingers 111, 112 and enclosure 101 are positionedopposite a cartridge 120 in the selected cartridge storage location 0,carriage 110 is transported to the opening in enclosure 101 to extendgripper fingers 112 through the opening in enclosure 101 to contactcartridge 120. If cartridge 120 and enclosure 101 are not in perfectalignment, finger gripper mechanism 127 is compliant and the contactingof gripper fingers 111, 112 with cartridge 120 causes finger grippermechanism 127 to be pulled in a direction that causes gripper fingers111, 112 to enclose the sides of the cartridge 120 therebetween. Thefinger gripper mechanism 127 then closes gripper fingers 111, 112 withsufficient force to securely grasp cartridge 120, at which time grippermechanism 127 is retracted into enclosure 101 by moving carriage 110 inthe -z direction. A misalignment between cartridge 120 and the centerlines V_(c), H_(c) of the opening in enclosure 101 causes cartridge 120to come into contact with the tapered segments 151-154 of guide fingers141-144 of guides 131-134 located along the inside corners of enclosure101. The tapered segments 151-154 of guide fingers 141-144 increase theeffective aperture presented to cartridge 120 by guides 131-134 and whencartridge 120 comes in contact with a tapered end 151-154 of a guidefinger 141-144, it causes compression of the associated spring 135-138to thereby align guide fingers 141-144 of guides 131-134 with acorresponding edge of cartridge 120. Attachment plates 145-148 provide amechanical stop to limit the movement of guide fingers 141-144 in both xaxis and y axis directions. Once the cartridge 120 clears cartridgestorage location 0, the force exerted by compressed springs 135-138 oncorresponding guide fingers 141-144 causes cartridge 120 to berepositioned to a location where the force exerted on cartridge 120 bythe plurality of guide fingers 141-144 is reduced to that which isrequired to support cartridge 120 in both x axis and y axis directions.This position of support force represents the center lines V_(c), H_(c)of the opening in both x axis and y axis directions. Springs 135-138 aredesigned to preload guide fingers 141-144 against attachment plates145-148 to form a pocket that is slightly larger than cartridge 120.Springs 135-138 do not act against each other when cartridge 120 isretrieved into this pocket, and cartridge 120 is free.

In addition to centering cartridge 120 within enclosure 101, guides131-134 also function to provide support to cartridge 120 as it isremoved from cartridge storage location 0, retrieved into enclosure 101,transported to a new location and deposited there. Therefore, the forcerequired to be applied to cartridge 120 by gripper fingers 111, 112 ofgripper mechanism 100 is reduced since gripper fingers 111, 112 do nothave to apply sufficient force to cartridge 120 to prevent its movementin both x axis and y axis directions. Instead, object storage location 0supports cartridge 120 as it is being extracted therefrom and fingergripper mechanism 127 simply holds cartridge 120 with sufficient forceto enable it to be extracted from object storage location 0. The end ofcartridge 120 facing gripper mechanism 100 encounters guide fingers141-144 located within enclosure 101 prior to cartridge 120 being fullyextracted from cartridge storage location 0 and cartridge 120 is thencesupported by guide fingers 131-134. Therefore, carriage 110 with itsfinger gripper mechanism 127 functions to slide cartridge 120 fromcartridge storage location 0 on to guide fingers 141-144 of guides131-134 of enclosure 101 and finger gripper mechanism 127 must thereforeonly provide sufficient gripping force on cartridge 120 to enablecartridge 120 to slide from one location to another in the -z axisdirection without the friction forces encountered in this operationcausing cartridge 120 to come free from finger gripper mechanism 127.

Carriage Mechanism

The substantially rectangular space encircled by guides 131-134represents the cartridge movement space and must remain clear of allobstructions in order to enable cartridge 120 to freely move in and outof enclosure 101. Therefore, finger gripper mechanism 127 is attached tocarriage 110 which is supported by a pair of tracks 102, 103 which arelocated within enclosure 101 and external to the cartridge movementspace defined by the position of guides 131-134. The tracks 102, 103 arelocated on opposite interior sides of enclosure 101 and extend from theopening end A to the interior rear end P of enclosure 101 in anorientation to enable finger gripper mechanism 127 to travel in -z axisand +z axis directions and centered in both x and y axes within theopening of enclosure 101. The use of a pair of tracks 102, 103 enablescarriage 110 to be supported along the full length of its travel in amanner that produces minimum friction force on the mechanism and yetsecurely supports finger gripper mechanism 127.

Finger gripper mechanism 127 is connected to a carriage 110 whichfunctions to transport finger gripper mechanism 127 between its fullyextended position at the opening end A of enclosure 101 to its fullyretracted position adjacent the rear interior wall end P of enclosure101. Carriage 110 extends from track 102 to track 103 and is slidablyconnected to tracks 102, 103. Tracks 102, 103 are U-shaped and receivethe substantially rectangular-shaped rail at either end of carriage 110.The tracks 102, 103 are manufactured of a material such as Vespel® (atrademark of DuPont, Inc.) to provide a surface, having a lowcoefficient of friction and requiring no lubrication, on which carriage110 rides. The U-shape of tracks 102, 103 also constrain the horizontal(x axis direction) and vertical (y axis direction) movement of carriage110 to thereby position carriage 110 along the horizontal (x axis)centerline H_(c) and vertical centerline V_(c) of enclosure 101.Carriage 110 functions to transport finger gripper mechanism 127 in thez axis direction, guided in the horizontal (x axis direction) and thevertical (y axis direction) along centerlines H_(c) and V_(c), therebyprecisely locating finger gripper mechanism 127 within enclosure 101.

Dual Belt Drive Mechanism

The distance of travel required of finger gripper mechanism 127 and thephysical space between the two concentric cylinders of cartridge storagelocations in which it must operate, requires that the tractor mechanismfor finger gripper mechanism 127 must be compact yet have a long stroke.Therefore, carriage 110 cannot be driven directly in line with itscenter of gravity but must be driven at an offset distance, parallel tobut outside of the object handling space. In prior systems, the tractormechanism was placed to one side of the object handling space, producinga moment on the carriage guide system. To compensate for this force,massive low friction, precision guides such as linear ball bearings wereused to support the carriage.

To implement the tractor mechanism in a low cost, simple manner, thetractor mechanism of the present embodiment uses a pair of tracks 102,103 symmetrically arranged with respect to carriage 110. The motivedrive is provided by dual timing belt drives which consist of toothedbelts 104, 105 driven by a single motor 128 located at the rear end P ofthe interior of enclosure 101. Drive motor 128 is attached to enclosure101 and drives shaft 129 oriented in the y axis direction and alignedwith respect to the opening. Drive shaft 129 is attached at its ends todrive gears 108, 109 which mate in well known fashion with the teeth ondrive belts 104, 105, respectively. Proximate to the opening ofenclosure 101 and at the distal end A of tracks 102, 103 is a pair offreely rotating idler pulleys 106, 107 which also engage toothed belts104, 105 such that belts 104, 105 form endless loops around gears 108,106 and 109, 107, respectively. Idler pulleys 106, 107 function totension toothed belts 104, 105 as well as define the end of travel ofcarriage 110. As drive motor 128 rotates drive shaft 129, drive gears108, 109 at either end thereof cause toothed belts 104, 105 to move insynchronized rotation to apply equal displacements to either end ofcarriage 110 on which finger gripper mechanism 127 rides along tracks102, 103. The toothed belts 104, 105 also enable drive motor 128 to veryprecisely position finger gripper mechanism 127 without slippage. Sideloads (x axis direction and y axis direction) on carriage 110 arereacted by the "U" shaped tracks 102, 103 as are yaw and roll moments.Pitch moments are reacted by the motor shaft through the pair ofsynchronized toothed belts 104, 105. This mechanism is simple andcompact yet reacts to any side loads, yaw/roll moments.

Toothed belts 104, 105 are attached to carriage 110 in a simple mannerthat does not require the use of fasteners (FIG. 9). A tab 130 isprovided in carriage 110 at either end thereof, juxtaposed to tracks102, 103. Tab 130 can be of any shape and as shown in FIG. 8 it issubstantially rectangularly shaped. On one side of tab 130, arranged ina straight line therewith, is a notch 126a through which the toothedbelt 104, 105 is fed. Thus, toothed belt 104, 105 enters notch 126a, iswrapped over tab 130 via notches 126b, 126c and exits notch 126a. Theteeth on toothed belt 104, 105 engage both tab 130 and each other asthey pass through notch 126a in carriage 110. This fixedly couplescarriage 110 to toothed belts 104, 105 without the use of fasteners. Itis evident that the orientation of tab 130 with regard to notch 126a isa matter of design choice and the linear arrangement of tab 130 andnotches 126a, 126b, 126c is shown herein as one of the numerous possibleconfigurations.

Finger Gripper Mechanism

The finger gripper mechanism 127 (FIGS. 3-5) itself consists of a pairof gripper fingers 111, 112 hingeably attached to either end of arectangular support structure 113. Therefore, by applying an outwardlydirected force to the interior ends I of gripper fingers 111, 112, thegripping end G of gripper fingers 111, 112 are caused to close oncartridge 120 placed therebetween, since gripper fingers 111, 112 pivotaround support structure 113. An outwardly or inwardly directed forceapplied to the interior ends I of gripper fingers 111, 112 causesgripper fingers 111, 112 to rotate around the hinged connection tosupport structure 113. The hinge mechanism is designed to be simplyassembled, requiring no lubricant, and freely moving. These goals areachieved by the use of a plurality of linearly arranged openings 121 ingripper fingers 111, 112, each of which mates with a correspondingprojection on support structure 113 to precisely position gripperfingers 111, 112 with respect to support structure 113 and thereforewith respect to each other. The projections on support structure 113 areT-shaped tabs 123 and elongated tabs 123a, the shoulders 124, 124a ofwhich determine the position of gripper fingers 111, 112 in twodimensions (x, y). The interconnection of gripper fingers 111, 112 andsupport structure 113 is accomplished by offsetting elongated tabs 123ain a z axis direction from T-shaped tabs 123 so that their shoulders124a and 124 are in alignment. Thus, T-shaped tabs 123 press againstopenings 121 in a +z axis direction while elongated tabs 123a pressagainst their openings 121 in a -z axis direction. This causes gripperfingers 111, 112 to snap fit with support structure 113. The T-shapedtabs 123 with shoulders 124 and elongated tabs 123a with shoulders 124aenable gripper fingers 111, 112 to rotate hingeably around supportstructure 113.

Hinge lines similar to those formed between gripper fingers 111, 112 andsupport structure 113 are formed between gripper finger 111 and loadinglinkage 117, between gripper finger 112 and loading linkage 116, andbetween gripper support 118 and loading linkages 116, 117. A compressioncoil spring 115 placed between gripper support 118 and support structure113 acts to separate these two elements and close gripper fingers 111,112 at gripper end G. This closure is accomplished because as supportstructure 113 moves in the +z axis direction with respect to grippersupport 118, gripper fingers 111, 112 also move in the +z axisdirection, thereby moving the outer ends of loading linkages 116, 117 inthe +z axis direction while the interior ends of loading linkages 116,117 remain in fixed position by their attachment to gripper support 118.This mechanical interconnection causes loading linkages 116, 117 torotate about their interior end attachment to gripper support 118,opening gripper fingers 111, 112 at interior end I and closing gripperfingers 111, 112 at gripper end G.

It is the angular relation of loading linkages 116, 117 with respect togripper support 1118 that produces the mechanical advantage for gripperfingers 111, 112 and makes gripper fingers 111, 112 grip tighter if aforce attempts to remove cartridge 120 from between gripper fingers 111,112. This mechanical advantage allows the use of a smaller spring 115 toclose gripper fingers 111, 112 and also a smaller solenoid 125 tocompress spring 115 and open gripper fingers 111, 112.

The opening of the gripper fingers 111, 112 is accomplished by solenoid125 translating support structure 113 in the -z axis direction. Thissupport structure 113 movement is translated by the interaction of thehinges of finger gripper mechanism 127 into x-axis direction motion. Inparticular, loading linkages 116, 117 couple the interior ends I ofgripper fingers 111, 112 to gripper support 118, thereby providing alinkage to translate the movement of solenoid arm 114 into fingermovement. Solenoid arm 114 is attached at one end to support structure113 and passes through an aperture 174 in gripper support 118. A coilspring 115 is placed coaxially around collar 115a which enclosessolenoid arm 114 to apply a force between gripper support 118 andsupport structure 113 to separate these two elements and close gripperfingers 111, 112 at gripper end G. Solenoid 125 overcomes this springforce to open gripper fingers 111, 112. Gripper support 118 includes twoarms 175, 176 which, along with compliance spring 119, attach fingergripper mechanism 127 to carriage 110. Loading linkages 116, 117 providea mechanical advantage in closing gripper fingers 111, 112. Therefore,the spring force that must be produced by spring 115 is smaller as issolenoid 125 which also required less power to operate.

Loading Linkages

Loading linkages 116, 117 consist of a cross bar 165 to which isattached a plurality (4) of fingers 161-164. Two fingers 162, 163include a T-shaped tab 123b at the distal end thereof to interconnectvia shoulder 124b with a corresponding hole 122 in gripper fingers 111,112. The remaining two fingers 161, 164 have rectangular-shaped tabs124c on the distal end thereof and shoulders 124c to engagecorrespondingly shaped slots 122a in gripper fingers 111, 112. Thefingers 161-164 are offset in a z-axis direction to press againstopenings 122, 122a in opposite directions (±z axis) to cause loadinglinkages 116, 117 to snap fit with gripper fingers 111, 112. TheT-shaped tabs 123b with their shoulders 124b and rectangular-shaped tabs123c with their shoulders 124c enable gripper fingers 111, 112 tohingeably rotate on fingers 161-164 of loading linkages 116, 117. Theother end of loading linkages 116, 117 is cross bar 165 which ishingeably attached to gripper support 118. Cross bar 165 includes tabs167, 168 and hole 166 which couple with projections 171, 172 and 173,respectively on gripper support 118. These elements not only positionloading linkages 116, 117 with respect to gripper support 118, but alsohingeably interconnect these elements.

In operation, solenoid 125 moves solenoid arm 114 in the -z axisdirection, causing support structure 113 to move in that direction.Loading linkages 116, 117 are connected to gripper support 118 whichremains stationary. As support structure 113 moves in a -z axisdirection, loading linkages 116, 117 pivot on gripper support 118 andpull the interior end I of fingers 111, 112 inwardly together as afunction of the distance of travel in the -z axis direction of supportstructure 113. In addition, by translating solenoid arm 114 in theopposite direction by spring 115, a return force is produced on theinterior end I of gripper fingers 111, 112 forcing them open with theamount of force substantially equal to that produced in the closingoperation.

A further enhancement provided by the use of loading linkages 116, 117located at the interior end I of gripper fingers 111, 112, is thatloading linkages 116, 117 cause the production of a gripping force whichis applied to the interior end I of gripper fingers 111, 112 as afunction of the magnitude of force that is applied to the cartridge 120in order to extract the cartridge 120 from between gripper fingers 111,112. Therefore, any tendency for cartridge 120 to slide from betweengripper fingers 111, 112 or to be forced therefrom by external forces,is automatically compensated for by the use of these loading linkages116, 117 which function to automatically apply a gripping force which isdependent upon the magnitude of force that is applied to retractcartridge 120 from gripper fingers 111, 112.

Variable Compliance Gripper to Carriage Interconnection

Gripper support 118 is compliantly attached to carriage 110 by centeringspring 119. Therefore, gripper fingers 111, 112 and support structure113 are supported by gripper support 118 but in a manner that enables acertain amount of flexibility in this coupling to enable gripper fingers111, 112 to translate in both x axis and y axis directions a minimalamount to account for misalignment of gripper fingers 111, 112 withcartridge 120. The loading linkages 116, 117 at the interior end I ofgripper fingers 111, 112 are hingeable attached to gripper support 118and the interior end I of gripper fingers 111, 112 in order to enableloading linkages 116, 117 to pivot as solenoid arm 114 is moved in andout by spring 115 and solenoid 125.

A centering spring 119 is used to provide a compliant interconnection offinger gripper mechanism 127 to carriage 110. The interconnection ofthese two elements is disclosed in further detail in FIG. 8. Grippersupport 118 includes two arms 175, 176 which have flanged ends 175a,176a to rest against face 183 of carriage 110. Face 183 includesprojection 181 which constrains flanged ends 175a, 176a of arms 175, 176from x axis and y axis motion. Centering spring 119 is U-shaped and alsoincludes flanges 184 on the ends of each arm 185, 186 thereof. Flanges184 fit over projection 181 from face 183 to hold gripper support 118against face 183 of carriage 110. Thus, centering spring 119 coversgripper support 118 on three sides and provides a mechanism to springload gripper support 118 in position against face 183 of carriage 110and centered in projection 181.

Any misalignment when gripper fingers 111, 112 contact cartridge 120causes a moment to be transmitted to gripper support 118 to rotategripper support 118 with respect to face 183 and projection 181 ofcarriage 110 to translate and realign gripper fingers 111, 112 withrespect to cartridge 120. Since gripper support 118 is spring loadedagainst face 183 of carriage 110, the transmitted moment causes grippersupport 118 to be rotated. The amount of rotation of gripper support 118is limited by centering spring 119, which gripper support 118 comes incontact with after a predetermined distance of travel (w). The extent ofmovement of gripper support 118 is therefore limited by the dimensionsof centering spring (arms 185, 186) and projections 181 from face 183 ofcarriage 110. Centering spring 119 snaps over projections 181 therebyconnecting finger gripper mechanism 127 to carriage 110 without usingfasteners.

When finger gripper mechanism 127 retrieves cartridge 120 into enclosure101, the misalignment between gripper fingers 111, 112 and cartridge 120that cause gripper support 118 to rotate and realign gripper fingers111, 112 is corrected by guides 131-134 which realign cartridge 120 andfinger gripper mechanism 128 With center lines V_(c), H_(c) ofenclosure. Guides 131-134 therefore allow gripper support 118 to realignitself with respect to face 183 of carriage 110.

While a specific embodiment of this invention has been disclosed, it isexpected that those skilled in the art can and will design alternateembodiments of this invention that fall within the scope of the appendedclaims.

I claim:
 1. In an object handling system that includes a roboticmanipulator for transporting objects, an object retrieval apparatus,located at an end of said robotic manipulator, for retrieving an objectfrom an object storage location comprising:means for gripping saidobject to securely hold said object; means for translating said grippingmeans in a direction to remove said object from its object storagelocation; means for flexibly connecting said gripping means to saidtranslating means to enable said gripping means to be displaceable withrespect to a predetermined locus on said translating means; and means,engagable with said object, for automatically positioning said object asit is removed from said object storage location to a position inalignment with said predetermined locus on said translating means,comprising:a plurality of rails, aligned parallel to each other andpositioned to form a pocket to receive said object.
 2. The apparatus ofclaim 1 wherein said flexibly connecting means is responsive to apositional misalignment between said object and said predetermined locuson said translating means for enabling said gripping means to displacewith respect to said translating means in a direction to compensate forsaid misalignment when said gripping means contacts said object.
 3. Theapparatus of claim 2 wherein said flexibly connecting meanscomprises:spring means attached to said gripping means for coupling saidgripping means to said translating means.
 4. The apparatus of claim 1wherein said positioning means translates said gripping means to aposition in alignment with said predetermined locus on said translatingmeans as said object is moved to said position in alignment with saidpredetermined locus on said translating means.
 5. The apparatus of claim1 wherein said object comprises a substantially rectangular shapedobject, said plurality of rails comprise four rails, aligned to contacta corresponding one of four edges of said substantiallyrectangular-shaped object as said substantially rectangular-shapedobject is withdrawn from said object storage location.
 6. The apparatusof claim 1 wherein said positioning means comprises:a plurality ofsprings, each of which is attached to a corresponding one of saidplurality of rails, deformable from a preloaded position substantiallyin alignment with said predetermined locus on said translating means bysaid object being loaded from said object storage location into saidpocket formed by said plurality of rails, and which apply a force tosaid object in a direction opposite said deformation to place saidobject substantially in alignment with said predetermined locus on saidtranslating means once said object is removed from said object storagelocation.
 7. The apparatus of claim 6 further comprising:means forenclosing said positioning means for providing a rigid frame ofreference for said positioning means; and wherein said of said pluralityof springs have a first end and a second end, where said first end isattached to said enclosing means and said second end is attached to saidcorresponding rail.
 8. The apparatus of claim 1 wherein each of saidrails has a first end, proximate to said object storage location, andtapered to funnel said object from said object storage location intocontact with said plurality of rails.
 9. In an object handling systemthat includes a robotic manipulator for transporting objects, an objectretrieval apparatus, located at an end of said robotic manipulator whichpositions said object retrieval apparatus opposite an object storagelocation, for retrieving an object from said object storage location,comprising:means for gripping said object to securely hold said object;means for translating said gripping means along a path of predeterminedextent from a first position juxtaposed to said object storage location,where said gripping means contacts said object, to a second position ina direction to remove said object from its object storage location,comprising:carriage means, having first and second ends, for translatingbetween said first and second positions when said object retrievalapparatus is positioned opposite said object storage location; first andsecond tracks aligned parallel to each other and parallel to said pathfor receiving said first and second ends of said carriage means to guidesaid carriage means along said path; first and second belt drive means,substantially coextensive with said first and second tracks,respectively, for displacing said carriage means in said direction,which is parallel to said first and second tracks, to cause saidcarriage means to move along said first and second tracks in saiddirection; means for driving said first and second belt means to producesaid displacement; and means for flexibly connecting said gripping meansto said carriage means to enable said gripping means to be displacedwith respect to a predetermined locus on said carriage means; and means,engageable with said object wherein said object comprises asubstantially rectangular-shaped object box-like structure, forautomatically positioning said object as it is removed from said objectstorage location to a position in alignment with a predetermined locuson said carriage means, comprising:a plurality of rails, alignedparallel to each other and positioned to form a pocket to receive saidsubstantially rectangular-shaped object.
 10. The apparatus of claim 9wherein said first and second belt drive means each comprises:a drivegear means rotatably connected to said driving means and locatedproximate said second position; an idler pulley means, rotatable, andlocated proximate said first position; toothed belt means, connected tosaid carriage means, forming a continuous loop encircling and engagingsaid drive gear means and said idler pulley means; and wherein saiddriving means rotates said drive gear means, engaging said toothed beltmeans which translates around said idler pulley means, displacing saidattached carriage means along said path.
 11. The apparatus of claim 9wherein said flexibly connecting means is responsive to a positionalmisalignment between said object and said predetermined locus on saidcarriage means for enabling said gripping means to translate withrespect to said carriage means in a direction to compensate for saidmisalignment when said gripping means contacts said object.
 12. Theapparatus of claim 11 wherein said flexibly connecting meanscomprises:spring means attached to said gripping means for coupling saidgripping means to said carriage means.
 13. The apparatus of claim 9wherein said positioning means enables said gripping means to align withsaid predetermined locus as said object is moved to said position inalignment with said predetermined locus on said carriage means.
 14. Theapparatus of claim 9 wherein said plurality of rails comprise fourrails, aligned to contact a corresponding one of four edges of saidsubstantially rectangular-shaped object as said substantiallyrectangular-shaped object is withdrawn from said object storagelocation.
 15. The apparatus of claim 9 wherein said positioning meanscomprises:a plurality of springs, each of which is attached tocorresponding one of said plurality of rails, deformable from apreloaded position substantially in alignment with said predeterminedlocus on said carriage means by said substantially rectangular-shapedobject being loaded from said object storage location into said pocketformed by said plurality of rails, and which apply a force to saidsubstantially rectangular-shaped object in a direction opposite saiddeformation to substantially center said substantiallyrectangular-shaped object in alignment with said predetermined locus onsaid carriage means once said substantially rectangular-shaped object isremoved from said object storage location.
 16. The apparatus of claim 15further comprising:means for enclosing said positioning means forproviding a rigid frame of reference for said positioning means; andwherein each of said plurality of springs have a first end and a secondend, where said first end is attached to said enclosing means and saidsecond end is attached to said corresponding rail.